Apparatus and method for enhanced color to color conversion

Abstract

The present invention changes a color corresponding to a source color to a destination color by initially selecting a target source color and a target destination color. The selected target source color is converted to a source hue value, a source chroma reference value, and a source lightness reference value, and the selected target destination color is converted to a destination hue value, a destination chroma reference value, and a destination lightness reference value. A circuit then generates a first set of source/destination chroma and a first set of source/destination lightness values representing source/destination chroma and lightness relationships, respectively, for sources values in a range from the source chroma and lightness reference values, respectively, to minimum source chroma and lightness values, respectively, using a first and third function, respectively. The circuit also generates a second set of source/destination chroma values and a second set of source/destination lightness values representing source/destination chroma and lightness relationships, respectively, for source values in a range from the source chroma and lightness reference values, respectively, to maximum source chroma and lightness values, respectively, using a second and fourth function, respectively. These values are stored. Received color data is converted to a color hue value, a color chroma value, and a color lightness value. A comparator determines if the color hue value corresponds to the source hue value. When the comparator determines that the color hue value corresponds to the source hue value, destination chroma and lightness values associated with the source chroma and lightness values, respectively, that corresponds to the color chroma and lightness values, respectively, are selected based on the stored source/destination chroma and lightness relationships, respectively. The destination hue value and the selected destination chroma and lightness values are converted into output color data representing the destination color.

What is claimed is: 
     
       1. A system for changing a color corresponding to a source color to a destination color, comprising: first input means for selecting a target source color and a destination color;   first converting means, operatively connected to said first input means, for converting the input target source color to a source hue value, a source chroma reference value, and a source lightness reference value and the input destination color to a destination hue value, a destination chroma reference value, and a destination lightness reference value;   first table means, operatively connected to said first converting means, for generating a first set of values representing a source to destination chroma relationship for sources values in a range from the source chroma reference value to a minimum source chroma value using a first function;   second table means, operatively connected to said first converting means, for generating a second set of values representing a source to destination chroma relationship for source values in a range from the source chroma reference value to a maximum source chroma value using a second function;   chroma memory means, operatively connected to said first and second table means, for storing the first set of values and the second set of values;   second input means for receiving color data;   second converting means, operatively connected to said second input means, for converting the received color data to a color hue value, a color chroma value, and a color lightness value;   comparing means, operatively connected to said first and second converting means, for determining if the color hue value corresponds to the source hue value;   chroma data generating means, operatively connected to said second converting means, said chroma memory means, and said comparing means, for selecting a destination chroma value associated with the source chroma value that corresponds to the color chroma value based on the source to destination chroma relationship stored in said chroma memory means when said comparing means determines that the color hue value corresponds to the source hue value;   third table means, operatively connected to said first converting means, for generating a third set of values representing a source to destination lightness relationship for values in a range from the source lightness reference value to a minimum source lightness value using a third function;   fourth table means, operatively connected to said first converting means, for generating a fourth set of values representing a source to destination lightness relationship for values in a range from the source lightness reference value to a maximum source lightness value using a fourth function;   lightness memory means, operatively connected to said third and fourth table means, for storing the third and fourth sets of values;   lightness data generating means, operatively connected to said second converting means, said lightness memory means, and said comparing means, for selecting a destination lightness value associated with the source lightness value that corresponds to the color lightness value based on the source to destination lightness relationship stored in said lightness memory means when said comparing means determines that the color hue value corresponds to the source hue value; and   third converting means, operatively connected to said lightness data generating means and said chroma data generating means, for converting the destination hue value and the selected destination chroma and lightness values into output color data representing the destination color.   
     
     
       2. The system as claimed in claim 1, wherein the first, second, third, and fourth functions are distinct polynomials having at least one degree. 
     
     
       3. The system as claimed in claim 2, wherein the first function is graphically represented by a locus of points that form a first straight line from the minimum source value to the source chroma reference value, the second function is graphically represented by a locus of points that form a second straight line from the maximum source value to the source chroma reference value, the third function is graphically represented by a locus of points that form a third straight line from the minimum source value to the source lightness reference value, and the fourth function is graphically represented by a locus of points that form a fourth straight line from the maximum source value to the source lightness reference value. 
     
     
       4. A system for changing a color corresponding to a source color to a destination color, comprising: first input means for selecting a target source color and a destination color;   first converting means, operatively connected to said first input means, for converting the inputted target source color to a source hue value, a source chroma reference value, and a source lightness reference value and the inputted destination color to a destination hue value, a destination chroma reference value, and a destination lightness reference value;   first table means, operatively connected to said first converting means, for generating a first set of values representing a source to destination lightness relationship for sources values in a range from the source lightness reference value to a minimum source lightness value using a first function;   second table means, operatively connected to said first converting means, for generating a second set of values representing a source to destination lightness relationship for source values in a range from the source lightness reference value to a maximum source lightness value using a second function;   lightness memory means, operatively connected to said first and second table means, for storing the first set of values and the second set of values;   second input means for receiving color data;   second converting means, operatively connected to said second input means, for converting the received color data to a color hue value, a color chroma value, and a color lightness value;   comparing means, operatively connected to said second converting means, for determining if the color hue value corresponds to the source hue value;   lightness data generating means, operatively connected to said comparing means, said second converting means, and said lightness memory means, for selecting a destination lightness value associated with the source lightness value that corresponds to the color lightness value based on the source to destination lightness relationship stored in said lightness memory means when said comparing means determines that the color hue value corresponds to the source hue value; and   third converting means, operatively connected to said lightness data generating means, for converting the destination hue value and the selected destination lightness value into output color data representing the destination color.   
     
     
       5. A system for changing a color corresponding to a source color to a destination color, comprising: first input means for selecting a target source color and a destination color;   first converting means, operatively connected to said first input means, for converting the inputted target source color to a source hue value, a source chroma reference value, and a source lightness reference value and the inputted destination color to a destination hue value, a destination chroma reference value, and a destination lightness reference value;   first table means, operatively connected to said first converting means, for generating a first set of values representing a source to destination chroma relationship for sources values in a range from the source chroma reference value to a minimum source chroma value using a first function;   second table means, operatively connected to said first converting means, for generating a second set of values representing a source to destination chroma relationship for source values in a range from the source chroma reference value to a maximum source chroma value using a second function;   chroma memory means, operatively connected to said first and second table means, for storing the first set of values and the second set of values;   second input means for receiving color data;   second converting means, operatively connected to said second input means, for converting the received color data to a color hue value, a color chroma value, and a color chroma value;   comparing means, operatively connected to said second converting means, for determining if the color hue value corresponds to the source hue value;   chroma data generating means, operatively connected to said comparing means, said second converting means, and said chroma memory means, for selecting a destination chroma value associated with the source chroma value that corresponds to the color chroma value based on the source to destination chroma relationship stored in said chroma memory means when said comparing means determines that the color hue value corresponds to the source hue value; and   third converting means, operatively connected to said chroma data generating means, for converting the destination hue value and the selected destination chroma value into output color data representing the destination color.   
     
     
       6. A method of electronically generating color destination values to be used in a color conversion process, comprising the steps of: (a) selecting a source color and a corresponding destination color;   (b) converting, electronically, the selected source color into first, second, and third source values representing a three-dimensional color space;   (c) converting, electronically, the selected destination color into first, second, and third destination values representing a same three-dimensional color space as produced in said step (b);   (d) generating a first set of second destination values corresponding to a source to destination relationship for second source values in a range from the second source value generated in said step (b) to a predetermined minimum second source value using a first function;   (e) generating a second set of second destination values corresponding to a source to destination relationship for second source values in a range from the second source value generated in said step (b) to a predetermined maximum second source value using a second function; and   (f) storing the first and second sets of second destination values in a memory as a look-up table to be used when converting color data corresponding to the selected source color to the selected destination color.   
     
     
       7. The method as claimed in claim 6, further comprising the steps of: (g) generating a first set of third destination values corresponding to a source to destination relationship for third source values in a range from the third source value generated in said step (b) to a predetermined minimum third source value using a third function;   (h) generating a second set of third destination values corresponding to a source to destination relationship for third source values in a range from the third source value generated in said step (b) to a predetermined maximum third source value using a fourth function; and   (i) storing the first and second sets of third destination values in a memory as a look-up table to be used when converting color data corresponding to the selected source color to the selected destination color.   
     
     
       8. The method as claimed in claim 7, wherein the second source value is a source lightness value, the third source value is a source chroma value, the second destination value is a destination lightness value, and the third destination value is a destination chroma value. 
     
     
       9. The method as claimed in claim 8, wherein the first, second, third, and fourth functions are distinct polynomials having at least one degree. 
     
     
       10. The method as claimed in claim 7, wherein the first function is graphically represented by a locus of points that form a first straight line from the predetermined minimum second source value to the second target source value, the second function is graphically represented by a locus of points that form a second straight line from the predetermined maximum second source value to the second target source value, the third function is graphically represented by a locus of points that form a third straight line from the predetermined minimum third source value to the third target source value, and the fourth function is graphically represented by a locus of points that form a fourth straight line from the predetermined maximum third source value to the third target source value. 
     
     
       11. A system for changing a color corresponding to a target source color to a destination color, comprising: first input means for selecting a target source color and a corresponding target destination color;   first converting means, operatively connected to said first input means, for converting the selected target source color into first, second, and third target source values representing a three-dimensional color space, the first target source value representing a source hue value, and the selected target destination color into first, second, and third target destination values representing the three-dimensional color space, the first target destination value representing a destination hue value;   second input means for receiving color data;   second converting means, operatively connected to said second input means, for converting the received color data into first, second, and third color values representing the three-dimensional color space, the first color value representing a hue value;   comparing means, operatively connected to said second converting means, for determining if the first color value corresponds to the first target source value;   second destination value generating means, operatively connected to said second converting means, for generating a second destination value using a first function when the second color value is in a range from the second source target value to a predetermined minimum second source value;   said second destination value generating means generating the second destination value using a second function when the second color value is in a range from the second source target value to a predetermined maximum second source value; and   output means, operatively connected to said second converting means and said comparing means, for generating output color data representing the destination color based on the first destination target value and the second destination value generated by said second destination value generating means when said comparing means determines that the first color value corresponds to the first source target value.   
     
     
       12. The system as claimed in claim 11, wherein the second source value is a source lightness value, the third source value is a source chroma value, the second destination value is a destination lightness value, and the third destination value is a destination chroma value. 
     
     
       13. The system as claimed in claim 11, wherein the first and second functions are distinct polynomials having at least one degree. 
     
     
       14. The system as claimed in claim 11, further comprising: third destination value generating means, operatively connected to said second converting means, for generating a third destination value using a third function when the third color value is in a range from the third target source value to a predetermined minimum third source value and for generating the third destination value using a fourth function when the third color value is in a range from the third target source value to a predetermined maximum third source value;   said output means generating output color data representing the destination color based on the first destination target value and the generated second and third destination values when said comparing means determines that the first color value corresponds to the first target source value.   
     
     
       15. The system as claimed in claim 14, wherein said second destination value generating means comprises: first calculating means, operatively connected to said first converting means, for generating a first set of second destination values corresponding to a source to destination relationship for second source values in a range from the second source value produced by said converter means to a predetermined minimum second source value using the first function;   second calculating means, operatively connected to said first converting means, for generating a second set of second destination values corresponding to a source to destination relationship for second source values in a range from the second source value produced by said converter means to a predetermined maximum second source value using the second function; and   a first memory, operatively connected to said first and second calculating means, to store the first set of second destination values and the second set of second destination values in a look-up table format and to output a value corresponding to the second color value;   said output means generating output color data representing the destination color based on the first destination target value and the second destination value outputted by said first memory when said comparing means determines that the first color value corresponds to the first target source value.   
     
     
       16. The system as claimed in claim 15, wherein said third destination value generating means comprises: third calculating means, operatively connected to said first converting means, for generating a third set of third destination values corresponding to a source to destination relationship for third source values in a range from the third source value produced by said converter means to a predetermined minimum third source value using the third function;   fourth calculating means, operatively connected to said first converting means, for generating a fourth set of third destination values corresponding to a source to destination relationship for third source values in a range from the third source value produced by said converter means to a predetermined maximum third source value using the fourth function; and   a second memory, operatively connected to said third and fourth calculating means, to store the third set of second destination values and the fourth set of second destination values in a look-up table format and to output a value corresponding to the third color value;   said output means generating output color data representing the destination color based on the first destination target value and the second and third destination value outputted by said first and second memories when said comparing means determines that the first color value corresponds to the first target source value.   
     
     
       17. The system as claimed in claim 16, wherein the first function is graphically represented by a locus of points that form a first straight line from the predetermined minimum second source value to the second target source value, the second function is graphically represented by a locus of points that form a second straight line from the predetermined maximum second source value to the second target source value, the third function is graphically represented by a locus of points that form a third straight line from the predetermined minimum third source value to the third target source value, and the fourth function is graphically represented by a locus of points that form a fourth straight line from the predetermined maximum third source value to the third target source value. 
     
     
       18. The system as claimed in claim 16, wherein the first and second functions are portions of a single function graphically represented by a locus of points forming a curve from the predetermined maximum second source value through the second target source value to the predetermined minimum second source value, and the third and fourth functions are portions of a single function graphically represented by a locus of points forming a curve from the predetermined maximum third source value through the third target source value to the predetermined minimum third source value. 
     
     
       19. A method of changing a color corresponding to a target source color to a destination color, comprising the steps of: (a) selecting a target source color and a corresponding target destination color;   (b) converting, electronically, the selected target source color into first, second, and third target source values representing a three-dimensional color space, the first target source value representing a source hue value, and converting, electronically, the selected target destination color into first, second, and third target destination values representing a same three-dimensional color space, the first target destination value representing a destination hue value;   (c) receiving color data and converting, electronically, the color data into first, second, and third color values representing the same three-dimensional color space, the first color value representing a hue value;   (d) determining if the first color value corresponds to the first target source value;   (e) generating a second destination value using a first function when the second color value is in a range from the second source target value to a predetermined minimum second source value;   (f) generating a second destination value using a second function when the second color value is in a range from the second source target value to a predetermined maximum second source value; and   (g) generating output color data representing the destination color based on the first destination target value and the generated second destination value when said step (d) determines that the first color value corresponds to the first source target value.   
     
     
       20. The method as claimed in claim 19, further comprising the steps of: (i) generating a third destination value using a third function when the third color value is in a range from the third target source value to a predetermined minimum third source value; and   (j) generating the third destination value using a fourth function when the third color value is in a range from the third target source value to a predetermined maximum third source value;   said step (g) generating output color data representing the destination color based on the first target destination value and the generated second and third destination values if said step (d) determines that the first color value corresponds to the first target source value and said step (h) determines that a gradation mode has been selected.   
     
     
       21. The method as claimed in claim 20, wherein the second source value is a source lightness value, the second destination value is a destination lightness value, the third source value is a source chroma value, and the third destination value is a destination chroma value. 
     
     
       22. The method as claimed in claim 20, wherein the first, second, third, and fourth functions are distinct polynomials having at least one degree. 
     
     
       23. The method as claimed in claim 20, wherein the first function is graphically represented by a locus of points that form a first straight line from the predetermined minimum second source value to the second target source value, the second function is graphically represented by a locus of points that form a second straight line from the predetermined maximum second source value to the second target source value, the third function is graphically represented by a locus of points that form a third straight line from the predetermined minimum third source value to the third target source value, and the fourth function is graphically represented by a locus of points that form a fourth straight line from the predetermined maximum third source value to the third target source value. 
     
     
       24. The system as claimed in claim 20, wherein the first and second functions are portions of a single function graphically represented by a locus of points forming a curve from the predetermined maximum second source value through the second target source value to the predetermined minimum second source value, and the third and fourth functions are portions of a single function graphically represented by a locus of points forming a curve from the predetermined maximum third source value through the third target source value to the predetermined minimum third source value. 
     
     
       25. A system for converting a color corresponding to a source color to a destination color, comprising: first input means for selecting a target source color and a corresponding target destination color;   first converting means, operatively connected to said first input means, for converting the selected target source color into a first target source value of a three-dimensional color space, the first target source value representing a source hue value, and the selected target destination color into a first destination value in a same three-dimensional color space, the first destination value representing a target destination hue value;   second input means for receiving color data;   second converting means, operatively connected to said second input means, for converting the received color data into first, second, and third color values representing the same three-dimensional color space, the first color value representing a color hue value;   first comparing means, operatively connected to said first and second converting means, for determining if the first color value corresponds to the first target source value;   second comparing means, operatively connected to said second converting means, for determining if the second color value is within a predetermined range of values;   second destination value table means, operatively connected to said first and second comparing means, for storing a plurality of second destination values, each second destination value corresponding to a second source value in a range from a predetermined minimum second source value to a predetermined maximum second source value;   said second destination value table means outputting a second destination value that corresponds to an input second color value, the input second color value being used as the second source value for determining the second destination value when said first comparing means determines that the first color value corresponds to the first target source value and said second comparing means determines that the second color value is within a predetermined range of values; and   color data generating means, operatively connected to said second destination value table means, for generating output color data representing the destination color based on the first destination value and the outputted second destination value.   
     
     
       26. The system as claimed in claim 25, further comprising: third destination value table means, operatively connected to said first and second comparing means, for storing a plurality of third destination values, each third destination value corresponding to a third source value in a range from a predetermined minimum third source value to a predetermined maximum third source value;   said third destination value table means outputting a third destination value that corresponds to an inputted third color value, the inputted third color value being used as the third source value for determining the third destination value when said first comparing means determines that the first color value corresponds to the first target source value and said second comparing means determines that the second color value is within a predetermined range of values;   said color data generating means generating output color data representing the destination color based on the first destination target value and the outputted second and third destination values.   
     
     
       27. The system as claimed in claim 26, wherein: said plurality of second destination values stored in said second destination table means represent first and second functions, the first function corresponding to a source to destination relationship for second source values in a range from a predetermined minimum second source value to a target second source value and the second function corresponding to a source to destination relationship for second source values in a range from the target second source value to a predetermined maximum second source value, the target second source value representing the second source value for the target source color; and   said plurality of third destination values stored in said third destination table means represent third and fourth functions, the third function corresponding to a source to destination relationship for third source values in a range from a predetermined minimum third source value to a target third source value and the fourth function corresponding to a source to destination relationship for third source values in a range from the target third source value to a predetermined maximum third source value, the target third source value representing the third source value for the target source color.   
     
     
       28. The system as claimed in claim 27, wherein the first, second, third, and fourth functions are distinct polynomials having at least one degree. 
     
     
       29. The system as claimed in claim 27, wherein the first function is graphically represented by a locus of points that form a first straight line from the predetermined minimum second source value to the second target source value, the second function is graphically represented by a locus of points that form a second straight line from the predetermined maximum second source value to the second target source value, the third function is graphically represented by a locus of points that form a third straight line from the predetermined minimum third source value to the third target source value, and the fourth function is graphically represented by a locus of points that form a fourth straight line from the predetermined maximum third source value to the third target source value. 
     
     
       30. The system as claimed in claim 27, wherein the first and second functions are portions of a single function graphically represented by a locus of points forming a curve from the predetermined maximum second source value through the second target source value to the predetermined minimum second source value, and the third and fourth functions are portions of a single function graphically represented by a locus of points forming a curve from the predetermined maximum third source value through the third target source value to the predetermined minimum third source value.